• Bulletin of the Korean Chemical Society
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• 제33권5호
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• pp.1541-1546
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• 2012

The early stages of bismuth (Bi) electrodeposition on glass carbon electrode from alkaline electrolyte were studied by cyclic voltammetry, chronoamperometry, scanning electron microscopy, atomic force microscopy and X-ray diffraction. The CV analysis showed that the electrodeposition of Bi was determined to be quasireversible process with diffusion controlled. The current transients for Bi electrodeposition were analyzed according to the Scharifker-Hills model and the Heerman-Tarallo model. It can be concluded that the nucleation and growth mechanism was carried out under a 3D instantaneous nucleation, which was confirmed by SEM analysis. The kinetic growth parameters were obtained through a nonlinear fitting. In addition, the Bi film obtaining at -0.86 V for 1 hour was of compact and uniform surface with good smoothness, small roughness and a very high purity. The Bi film were indexed to rhombohedral crystal structure with preferred orientation of (0 1 2) planes to growth.

• Nuclear Engineering and Technology
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• 제53권4호
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• pp.1323-1330
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• 2021

This work reported the radiation shielding characteristic of the bismuth titanium vanadium sodium tellurite glass system. The density of the specially-developed glass samples was increased from 2.21 to 4.01 g/cm³ with the addition of Bi₂O₃, despite the fact the molar volume is decease within 85.43-54.79 cm³/mol. The WinXcom program was used to approximate the effect of Bi₂O₃ on the gamma radiation shielding parameters of bismuth titanium vanadium sodium tellurite glasses. The ㎛ values decrease with the increase of Bi₂O₃ concentration. The computed data shows that the glass sample with 20 mol.% of Bi₂O₃ content has the greatest radiation attenuation performance in comparison to other selected glasses. The Bi₂O₃-TiO₂-V₂O₅-Na₂O-TeO₂ glass system shows excellent neutron shielding material with high long-term light transmittance and discharge resistance and could be potentially used as transparent radiation-resistant shielding glass applications.

• Korean Chemical Engineering Research
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• 제58권3호
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• pp.486-492
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• 2020

가시광 LED 빛에 반응하는 페로브스이트형 bismuth ferrite (BFO) 광촉매 제조방법과 가시광 광촉매 반응 특성을 조사하였다. BFO는 졸-겔법에 따라 제조하였다. 제조된 BFO는 주로 BiFeO₃ 구조로 이루어져 있으며 Bi₂₄Fe₂O₃₉ 구조도 포함한 나노 크기의 결정을 이루고 있었다. BFO 나노 결정은 약 600 nm까지 자외선과 가시광선을 흡수하는 것을 UV-visible 확산 반사 스펙트럼으로부터 확인하였다. 확산 반사 스펙트럼으로부터 구한 BFO의 밴드갭은 약 2.2 eV로 나타났다. 포름알데히드는 585 nm와 613 nm 파장의 가시광 LED 램프의 빛과 BFO 광촉매와의 광반응에 의하여 분해되어 제거되었다. BFO의 가시광 LED 빛에서 광촉매 활성은 BFO의 좁은 밴드갭에서 기인하는 것으로 보인다.

• 자원리싸이클링
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• 제21권5호
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• pp.65-71
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• 2012

용융 PbO-$SiO_2$계 슬래그와 Bi를 $775{\sim}850^{\circ}C$의 마그네시아 도가니 중에서 평형시켜 Pb와 Bi의 평형분배에 대하여 조사하였다. 분위기 중의 산소분압은 $P_{CO2}/P_{CO}$의 비율을 조정하여 제어하였다. Pb의 분배비인 (%PbO)/[%Pb]는 슬래그 중의 $SiO_2$ 농도가 증가함에 따라 증가하였으며, Bi의 분배비인 ($%Bi_2O_3$)/[%Bi]는 슬래그 중의 $SiO_2$ 농도가 증가함에 따라 감소하였다. 그리고 반응 온도가 높을수록 금속 상중의 Pb 농도는 증가하였다. 이러한 결과는 열역학적으로 예측한 결과와 잘 일치하였다.

• 한국자기학회지
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• 제18권1호
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• pp.14-18
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• 2008

본 연구에서는 Bi:YIG($Bi_{0.5}Y_{2.5}Fe_5O_{12}$) 막을 에어로졸 성막법을 이용하여 제작함에 있어서, 에어로졸을 구성하는 수송가스의 유량이 막의 자기적 특성과 광학적인 특성에 대하여 분석하였다. 직경 $100{\sim}500$ nm 의 Bi:YIG 분말을 질소 가스를 수송가스로 사용하여 성막을 실시하였고, 이 때, 수송가스의 유량은 0.5 l/min${\sim}10$ l/min 사이에서 변화시켰다. 수송가스의 유량이 증가할수록 Bi:YIG 막의 보자력은 51 Oe에서 37 Oe까지 지수함수적으로 감소하였다. 이것은 충돌에너지가 증가함에 따라 막내부 혹은 막표면의 결함이 감소하였기 때문이라고 고찰되었다. 포화자화는 유량이 증가할수록 감소하였는데, 이는 충돌에너지가 강해짐에 따라 결정이 왜곡되는 힘을 받았기 때문이라고 고찰되었다.

• 한국재료학회지
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• 제16권5호
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• pp.292-296
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• 2006

Effects of rapid thermal annealing of bismuth telluride thin films on their thermoelectric properties were investigated. Films with four different compositions were elaborated by co-sputtering of Bi and Te targets. Rapid thermal treatments in range of $300{\sim}400^{\circ}C$ were carried out during 10 minutes under the reducing atmosphere (Ar with 10% $H_2$). As the temperature of thermal treatment increased, carrier concentrations of films decreased while their mobilities increased. These changes were clearly observed for the films close to the stoichiometric composition. Rapid thermal treatment was found to be effective in improving the thermoelectric properties of $Bi_2Te_3$ films. Recrystallization of $Bi_2Te_3$ phase has caused the enhancement of thermoelectric properties, along with the decrease of the carrier concentration. Maximum values of Seebeck coefficient and power factor were obtained for the films treated at $400^{\circ}C$ (about $-128{\mu}V/K$ and $9{\times}10^{-4}\;W/K^2m$, respectively). With further higher temperature ($500^{\circ}C$), thermoelectric properties deteriorated due to the evaporation of Te element and subsequent disruption of film's structure.

• 한국진공학회지
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• 제14권4호
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• pp.215-221
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• 2005

비스무스와 텔루리움 타겟을 co-sputtering하여 열전특성을 지닌 비스무스 텔루라이드($Bi_2Te_3$) 박막을 제조하고, 증착온도에 따른 표면형상, 결정성, 그리고 전기적 특성의 변화를 조사하였다. 표면온도가 $290^{\circ}C$ 이상일 때, 박막의 표면에서 육각형상의 결정이 뚜렷이 관찰되었으며, X선 회절분석을 통하여 높은 증착온도에서 박막의 주된 구성물질이 rhombohedral 구조의 $Bi_2Te_3$ 결정상에서 hexagonal 구조의 BiTe 결정상으로 변하는 것을 확인하였다. 높은 증착온도에서 제조된 박막의 조성이 $Bi_2Te_3$의 화학양론비에서 벗어남으로 구조적 변화와 함께 전기적 특성도 변한다는 사실을 알 수 있었다. 제조된 비스무스 텔루라이드 박막의 열전특성을 파악하기 위해 제벡계수(Seebeck coefficient)를 측정하였다. 모든 시편이 n타입의 열전박막임을 확인하였으며, 증착온도 약 $225^{\circ}C$에서 열전특성의 최적값 (제벡계수: -55 $\mu$V/$K^{2}$, 열전성능인자: $3\times10^{-4}$ W/$k^{2}$m)이 얻어졌다. 그 이상의 온도에서 나타나는 열전 특성의 저하는 텔루리움의 증발에 따른 $Bi_{2}$$Te_{3}$ 열전박막의 텔루리움 함량 부족과 그에 따른 BiTe 결정상의 발생으로 이해된다.

• 한국분말재료학회지
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• 제20권5호
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• pp.345-349
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• 2013

Carbon nanotube-dispersed bismuth telluride matrix (CNT/$Bi_2Te_3$) nanopowders were synthesized by chemical routes followed by a ball-milling process. The microstructures of the synthesized CNT/$Bi_2Te_3$ nanopowders showed the characteristic microstructure of CNTs dispersed among disc-shaped $Bi_2Te_3$ nanopowders with as an average size of 500 nm in-plane and a few tens of nm in thickness. The prepared nanopowders were sintered into composites with a homogeneous dispersion of CNTs in a $Bi_2Te_3$ matrix. The dimensionless figure-of-merit of the composite showed an enhanced value compared to that of pure $Bi_2Te_3$ at the room temperature due to the reduced thermal conductivity and increased electrical conductivity with the addition of CNTs.

• 산업기술연구
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• 제24권B호
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• pp.59-64
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• 2004

GaAs thin films were grown epitaxially by MOCVD method on (001) GaAs substrate. And as a surfactant, Bi(bismuth) thin films were deposited on GaAs buffer layer by using TMBi(trimethylbismuth) source. In-situ reflectance difference spectroscopy(RDS) was used to monitor the surface reconstruction of GaAs and Bi thin films. As the results, under the exposure of TBAs(tertiarybuthylarsine) and hydrogen atmosphere, the surface reconstruction of GaAs was changed from As-rich c($4{\times}4$) to As-rich ($2{\times}4$), which was due to the adsoption and desorption of As dimers. The first bismuth surface related RDS signal was reported. At the deposition temperature of $450^{\circ}C$, Bi-terminated GaAs surface showed the RDS spectrum similar to that of Sb-terminated GaAs surface, possibly a ($2{\times}4$) surface. And Bi surface layers were rapidly evaporated with increasing the deposition temperature($550^{\circ}C$), finally becoming As-terminated ($2{\times}4$) surface.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2000년도 하계학술대회 논문집
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• pp.193-197
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• 2000

BSCCO thin films are fabricated via a co-deposition process by an ion beam sputtering with an ultra-low growth rate, and sticking coefficients of the respective elements are evaluated. The sticking coefficient of Bi element exhibits a characteristic temperature dependence : almost a constant value of 0.49 below 73$0^{\circ}C$ and decreases linearly with temperature over 73$0^{\circ}C$. This temperature dependence can be elucidated from the evaporation and sublimation rates of bismuth oxide, Bi$_2$O$_3$, from the film surface. It is considered that the liquid phase of the bismuth oxide plays an important role in the Bi(2212) phase formation in the co-deposition process.